Chemical vapor deposition (CVD) of films and plasma dry etching are extensively used in the semiconductor industry for fabricating integrated circuits on semiconductor wafers. Plasma enhanced CVD is one of the CVD methods used for thin film formation.
The deposition and etching processes are generally performed in a single-wafer reactive chamber. Inside the chamber, a reactant processing gas for film formation or etching is introduced through a shower head over the wafer. The reactant processing gas may or may not be transformed into plasma before striking the semiconductor wafer.
Non-uniformity of a chemical vapor deposited film or the etching in the desired areas can damage device structures and reduce the chip yield in the semiconductor fabrication. For example, deposition of a thin film at an Angstroms or nanometer level of thickness should be precisely controlled. Localized over-etching of the underlying layer should also be avoided.
Meanwhile, the size of semiconductor wafers has gradually increased to improve throughput and reduce cost per die. For example, in the transition from 300 mm to 450 mm wafer size, the wafer area increases by 125%. The within wafer uniformity (WiWU) becomes more difficult to maintain in the more-than-double-sized wafer.